The manner in which genes are organized (arranged) and packaged in the nucleus plays a major role in their subsequent expression in vivo. Recently several kinds of experiments have led to the view that chromatin exists as a regularly repeating structure. The repeating units (nucleosomes, nu bodies) contain 130-140 base pairs of DNA wound around a histone core and nonhistone proteins. The role of the nucleosomes in the regulation of gene activity has been established and will be investigated here. The objectives are to determine (1) if transcription can be initiated on nucleosomes, (2) if the nucleosome structure is changed during a transcription event, and (3) whether nonhistone proteins contained in nucleosomes can modulate the rate of RNA synthesis in vitro. Nucleosomes prepared from human placental chromatin by nuclease digestion will be transcribed by E. coli RNA polymerase under conditions where reinitiation is blocked. The quantity and quality of initiation sites will be assessed. The role of nucleosomal nonhistone proteins on transcriptional control will be examined by reconstitution experiments. The experiments described here will elucidate the relationship between nucleosome structure and function.